Lab Report 9 - Reactants and products – An online Simulation “I am in equilibrium” PDF

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Reactants and products – An online Simulation “I am in equilibrium”...

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Reactants and products – An online Simulation “I am in equilibrium” 1.0

Introduction In this lab, we created different equilibrium reactions using a Java computer simulation. The general formula for the reaction was R+Y⇌B+G, which means that red particles and yellow particles react to make blue and green particles, and vice versa. Using the simulation, we were able to alter the starting concentration of each particle and edit the rate of the forward and backward reaction. Changing these parameters, we were able to discover if and how they may affect the equilibrium reaction. Additionally, calculated the equilibrium constant for every reaction with different parameters. Then, we tried to create equilibrium reactions that would take a long time to reach equilibrium, have a high yield, and are mostly products at equilibrium, which is reached quickly. Lastly, we designed experiments that confirmed le Châtelier’s Principle.

2.0 Materials -

Computer

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Ruler

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Java Simulation

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Calculator

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Lab Manual

3.0 Observation and Experimental Part Two and Three: Observations Trial 1: -

The red and yellow particles react very quickly at first, then the reaction slows down and the last couple of red and yellow particles react very slowly.

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The green and blue particles appear very rapidly and do not react with each other.

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When the rate of the reverse reaction is zero, the reverse reaction does not occur, which explains why there were almost only blue and green particles when the reaction reached equilibrium and almost no yellow or red particles.

Trial 2: -

Equilibrium is reached very quickly.

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Reactions happen continuously and does not stop after equilibrium is reached.

Trial 3: -

Equilibrium is reached very quickly.

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Reactions happen continuously and does not stop after equilibrium is reached.

Trial 4: -

Equilibrium is reached very quickly.

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Concentrations are almost constant throughout simulation.

Trial 5: -

There is always more blue and yellow than red and green.

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Reactions happen continuously.

Graphs and Dimensions

Trial 1:

Trial 3:

Trial 2:

Trial 4:

Trial 5:

Data Trial [R] [Y] [G] [B] # Initial Initial Intitial Initial k_f 1 100 100 0 0 1 2 100 100 0 0 0.3 3 0 0 100 100 0.3 4 50 50 50 50 0.3 5 30 70 10 50 0.3

[R] [Y] [G] [B] Time to eq eq eq equilibrium k_r eq K 0 0 0 100 100 01:18.9 10000 0.1 26 26 73 73 00:09.1 8 0.1 13 13 78 78 00:09.5 40 0.1 20 20 79 79 00:11.4 20 0.1 13 53 30 71 00:11.7 3

Calculations Equilibrium Constant Expression = 𝐾1 =

[𝐵][𝐺] [𝑅 ][𝑌]

(99𝑀)(99𝑀) = 9801~10000 (1𝑀)(1𝑀)

𝐾2 =

(73𝑀)(73𝑀) = 7.88~8 (26𝑀)(26𝑀)

𝐾3 =

(78𝑀)(78𝑀) = 36~40 (13𝑀)(13𝑀)

𝐾4 =

(79𝑀)(79𝑀) = 15.6~20 (20𝑀)(20𝑀)

𝐾5 =

(71𝑀)(30𝑀) = 3.09~3 (13𝑀)(53𝑀)

Part Four: Observations a) Takes a long time to establish equilibirum b) A high yield is obtained c) Moslty products at equilibrium and equilibirum is reached quickly Graphs and Dimentions a)

b)

c)

Part Five: Graphs and Dimensions

Trial 1:

Trial 2:

Trial 3:

Data Trail #

[R] Initial

[Y] Initial

[G] Intitial

[B] Initial

k_f

k_r

[R] eq

[Y] eq

[G] eq

[B] eq

K

1 2 3

50 100 50

50 100 50

50 50 100

50 0.3 50 0.3 100 0.1

0.3 0.1 0.3

50 57 91

50 57 91

50 93 62

50 93 62

1 3 0.5

4.0 Discussion and Conclusion As observed in part 3 of this experiment, the equilibrium constant, K, does not depend on initial concentrations, rather it depends on the concentrations that the substances have at equilibrium. If the rate of the forward reaction is larger than the rate of the backwards reaction, there will be more products at equilibrium, which will then result in a larger K. If the backward reaction had a higher rate than the forward reaction, there would be more reactants at equilibrium, which would result in a smaller K value. In part 4 we can see that to make a reaction take long time to reach equilibirum have a very small initial concentration, and a low forward and backward reaction rate. If a reaction should have high yield, the forward reaction should be much faster than the backward reaction, which will result in a lot of product. Lastly, to have mostly products at equilibirum, the forward reaction rate should be a large number and backward reaction rates should be a small number. This would mean that the numerator of the equilbrium constant equation would be very large and the denominator would be very small. This would make K>1 and there would be more product. Additionally, the starting concentration should be equal for both reactants and products. In part 5 we can see, that as predicted by le Chatelier’s Principles, if we add product, the reactants will be increase at equilibrium, and if we add reactants, the products will increase at equilibrium. 5.0 Focus Questions 1. Do you agree or disagree with the following statements? (Support your answer with observations and results from this lab. a. “At equilibrium nothing is happening” i. Disagree, at equilibrium the reaction continues to happen, although the forward and backward reactions happen at the same time. This is seen in all the graphs above, as the concentrations of the substances continue to fluctuate, even after equilibrium is reached. b. “The equilibrium constant of a particular reaction depends on initial concentrations.”

i. Disagree, the equilibrium constant depends on the concentrations of the substances at equilibrium, not the initial concentrations. This can be observed in the table from part three. 2. What is the relationship between K and the rate constants? The equilibrium constant (K) is equal to the rate of the forward reaction (k_f) divided by the rate of the backward reaction (k_b). 6.0 References Smeureanu, Gabriela. “Experiment 9 Reactants and products – An online Simulation ‘I am in equilibrium’” Chemistry 106 General Chemistry Laboratory, edited by Stephanie Geggier, Custom Publishing, Inc., 2019, pp. 65-71.

7.0 Post Lab Questions 1. In an experiment to study the formation of HI(g), H2(g)+I2(g) →2HI(g), H2(g) and I2(g) were placed in a sealed container and allowed to react. On one set of axes, sketch concentration vs. time curves for H2 and HI. Account for the fact that there are more products than reactants in this reaction, when equilibrium is reached at room temperature. Explain the concept of dynamic equilibrium.

Equilibrium

Concentration (M)

2

H2(g)+I2(g)→2HI(g) 2HI(g)

1

H2(g) 0 0

Time (s)

Dynamic equilibrium is when the forward and backward reactions occur at the same rates. This means that the substances involved go back and forth between products and reactants, however, there is no overall change in concentration.

2. In another study of the formation of HI(g), H2(g) and I2(g) were placed in a sealed container at a certain temperature. At equilibrium, pH2=2.4*10-2atm, pI2=4.5*10-3atm, and pHI=3.6*10-1atm. Calculate K for this reaction. 𝑝𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 𝐾= 𝑝𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 𝐾=

(3.6 ∗ 10−1 )2 = 𝟏𝟐𝟎𝟎 (2.4 ∗ 10 −2)(4.5 ∗ 10−3)

The K of this reaction is 1200. 3. In the online simulation you could easily change concentrations and rate constants. In real life in the laboratory, you can change the initial concentrations of the species involved in a reaction, however, you cannot “set” the rate constants for a reaction. Rate constants are constants for a reaction, but they depend on one parameter. Which one? In a real experiment, how can you increase rate constants? How can you increase K? Rate constants depends on the temperature that the reaction takes place in. To increase the rate constant, you can increase the temperature or add a catalyst to the reaction. How to increase K depends on whether the reaction is endothermic or exothermic. If the reaction is endothermic and you want to increase K you have to increase the temperature, since heat is a reactant in this case and if you increase a reactant the reaction will shift towards the products, increasing K. If a reaction is exothermic you to decrease temperature, since it is a product and if you decrease a product the reaction will shift towards the products, increasing K....